Lithospheric slab tearing, the process by which a subducted lithospheric plate is torn apart and sinks into the Earth’s mantle, has been proposed as a cause for significant surface vertical motions. However, little is known about the mechanisms that help initiate slab tearing and the consequential topographic changes. This study aims to explore this process by means of 3D thermo-mechanical modelling. We use the Gibraltar Arc region (Betics Cordillera) as a reference scenario of continental collision where such tearing-uplift interaction has been proposed. Our results suggest that the obliquity of the continental passive margin (relative to the trench axis) is a major influence on the initiation of slab tearing because it promotes a laterally diachronous continental collision, which leads to earlier tearing inception in one end of the slab. As a result of this, the model results predict an east-to-west slab tearing (tearing velocity 37.6–67.6 cm/yr with the lower-mantle viscosity of up to 1e+22 Pa·s). While the fast slab tearing (<2 Myr over 600 km wide slab) and the lack of arcuate slab in our models limit a direct comparison with the Western Mediterranean, this approach provides a new insight into the link between slab tearing in the mantle and surface uplift. Our models yield uplift rates of 0.23–2.16 mm/yr in response to slab tearing. This range is compatible with the uplift rate needed to achieve an equilibrium between seaway-uplift and seaway-erosion, which could have led to the closure of marine gateways during the onset of the Messinian Salinity Crisis.